This invention represents a quantum leap advance in the technology that was first disclosed in my recently issued U.S. Pat. No. 4,681,439 dated July 21, 1987 and entitled "Pipe Laying Method and Apparatus".
As can be seen by reference to the above cited patent, as well as U.S. Pat. Nos: 3,631,601; 4,030,832; 3,907,435; 3,857,639; and 4,272,191, the prior art is replete with myriad and diverse approaches designed to simplify the task of laying pipe strings.
While all of the aforementioned prior art methods and apparatus are more than adequate for the purpose of accomplishing the end result for which they were designed and developed, these prior art patents are uniformly deficient with respect to the number of distinct structural components that are required to carry out their designated task.
A brief review of the prior art patents will quickly reveal that virtually all of the arrangements previously employed to lay a string of pipe require the use of at least two independent and structurally distinct elements to accomplish their stated goal. One of these components is designated as a centerline target and is intended and designed to be centrally disposed within the interior of a pipe segment; while the other component is designated as a grade checker, which is to be deployed at a spaced location from the pipe segment that contains the centerline target.
Obviously there has existed a long standing and as yet unsatisfied need for a single device that could perform the function and purpose of both a centerline target and a grade checker. However, it is equally obvious that none of the aforementioned prior art constructions even remotely envisioned that it would be possible to develop such a multi-function combined centerline target and grade checker apparatus.